The present invention relates to a multipole circuit breaker provided with a mechanism pole having a switching mechanism and adjacent poles, each disposed in opposition to the mechanism pole with an interphase wall disposed therebetween and each having an internal attachment such as an alarm switch or the like but having no switching mechanism.
FIGS. 1 through 5 show a conventional multipole circuit breaker as disclosed, for example, in Japanese Utility Model application No. 61-122792, of which FIG. 1 is a front view, FIG. 2 is an enlarged cross section taken on a line II--II in FIG. 1, FIG. 3 is an enlarged cross section taken on a line III--III in FIG. 1, FIG. 4 is a partial view of FIG. 2 showing a tripped state, FIG. 5 is a partial view of FIG. 3 showing a striped state, FIG. 6 is a perspective view of the supporting shaft with the lever attached thereon, FIG. 7 is a sectional view taken on line VII--VII in FIG. 6, and FIG. 8 is a perspective view of the supporting shaft.
In these drawings, a circuit breaker casing 1, constituted by a base 1a and a cover 1b, is provided with a pole 1A having a switching mechanism and an adjacent pole 1B having an alarm switch but having no switching mechanism. Reference numeral 2 designates a power source side fixed electric conductor fixed on the base 1a, 3 designates a fixed contact fixedly attached to the fixed electric conductor 2, and 4 designates an automatic tripping device in which, for example, a mechanism (not shown) of the thermal electromagnetic type or of the electronic type is employed. Reference numeral 5 designates a load side fixed electric conductor connected to the automatic tripping device 4, 6 designates a movable contact, 7 designates a moving element to which the movable contact 6 is fixed, 8 designates a flexible electric conductor for connecting the moving element 7 to the automatic tripping device 4 through a connecting electric conductor 9, and 10 designates a contact arm for holding the moving element 7. The contact arm 10 is divided into a first contact arm 10a connected to a switching mechanism (described below) and a second contact arm 10b for rotatably supporting the moving element 7 with a first pin 11. Reference numeral 12 designates a supporting shaft of the contact arm 10 for rotatably supporting the first and second contact arms 10a and 10b. Reference numeral 13 designates a crossbar for connecting the first contact arms 10a of the poles to each other, 14 designates a guide hole formed through the first contact arm 10a extending in the circuit breaking direction, and 15 designates an elongated hole formed through the second contact arm 10b extending transversely to the guide hole 14. Reference numeral 16 designates a second pin engaged between the guide hole 4 and the elongated hole 15, and 17 designates an tension spring provided between the first and second pins 11 and 16 which provides a spring force on the second pin 16. Reference numeral 18 designates a pressing spring provided between the moving element 7 and the second contact arm 10b, 19 designates an operating handle of the breaker, and 20 designates a switching mechanism of the breaker constituted by a cradle 20a, an upper link 20b, and a lower link 20c. Reference numeral 21 designates a stopper pin provided on the cradle 20a, 22 designates a connecting pin for connecting the lower link 20c to the first contact arm 10a, 23 designates an arc-extinguishing chamber, and 24 designates a latch rotatably supported by a supporting shaft 25 for engaging with the cradle 20a. Reference numeral 26 designates a trip bar latch of the automatic tripping device 4 engaged with the latch 24 through a latch lever 27. Reference numeral 28 designates circular holes formed through interphase walls 1c of the breaker casing 1 through which passes the supporting shaft 25a, 25A and 29 designates a lever fixed on the supporting shaft 25a, 25A so as to engage the cradle 20a at the lower side. Reference numeral 30 designates a torsion spring for continuously urging the lever 29 in the direction for tripping the cradle 20a (that is, in the direction of an arrow 31), 32 designates an alarm switch for operating an alarm lamp, a buzzer, etc. when the circuit breaker is tripped, and 33 designates an actuator fixed on the supporting shaft 25 so as to engage with the alarm switch 32.
Next, a description will be made as to the operation of the circuit breaker. In the On state of the switching mechanism pole 1A shown in FIGS. 1 and 2, a current flows in the following path: the power source side fixed conductor 2.fwdarw.the fixed contact 3.fwdarw.the movable contact 6.fwdarw.the moving element 7.fwdarw.the flexible conductor 8.fwdarw.the connecting conductor 9.fwdarw.the automatic tripping device 4.fwdarw.the load side fixed conductor 5. In the ON state of the adjacent electrode 1B shown in FIGS. 1 and 3, on the other hand, a current flows in the following path: the power source side fixed conductor 2.fwdarw.the fixed contact 3.fwdarw.the movable contact 6.fwdarw.the moving element 7.fwdarw.the flexible conductor 8.fwdarw.the connecting conductor 9.fwdarw.the load side fixed conductor 5. When the operating handle 19 is set to the OFF state (in the direction of an arrow 34 in FIG. 2), the contact arm 10 is lifted by the switching mechanism 20, and the movable contact 6 is disconnected from the fixed contact 3 together with the moving element 7. At this time, since the second pin 16 is fitted in a recess portion 14 a of the guide hole 14 by the tension spring 17, the second contact arm 10b is lifted by the switching mechanism 20 together with the first contact arm 10a. As a result, the second contact arm 10b rotates about the supporting shaft 12 and collides with the stopper pin 21 to thereby stop rotating. The rotation of the first contact arm 10a is transmitted to the first contact arm 10a of the adjacent pole 1B in FIG. 3 through the crossbar 13, and the contact arm 10 of the adjacent pole 1B is lifted in the same manner as in the switching mechanism pole 1A to thereby disconnect the movable contact 6 from the fixed contact 3 together with moving element 7.
When an overcurrent flows in the ON state depicted in FIGS. 1 and 2, the automatic tripping device 4 is actuated to rotate the latch 24 through the trip bar latch 26 and the latch lever 27 so that the cradle 20a is released from the latch 24 so as to jump up in the direction of the arrow 31 of FIG. 2. As a result, the contact arm 10 is lifted by the operation of the switching mechanism 20, and the movable contact 6 is disconnected so as to be tripped. Also at this time, the rotation of the first contact arm 10a is transmitted to the first contact arm 10a of the adjacent pole 1B in FIG. 3 through the crossbar 13, and the contact arm 10 of the adjacent pole 1B is lifted in the same manner as in the switching mechanism pole 1A so that the movable contact 6 is disconnected or tripped as shown in FIG. 5. When the cradle 20a is released from the latch 24 to jump up in the direction of the arrow 31, the lever 29 is rotated by the spring force of the torsion spring 30 in the direction of an arrow 35 in FIG. 2 so that the pole 1A is set in a tripped state as shown in FIG. 4. Further, the rotation of the lever 29 is transmitted to the actuator 33 through the supporting shaft 25 to thereby rotate the actuator 33 in the direction of an arrow 36 of FIG. 3 so that the adjacent pole 1B is set in a tripped state in FIG. 5 to thereby change over the connection of the alarm switch 32, that is, to generate an alarm informing that the breaker has been tripped.
Further, when a large current such as a short-circuit current or the like flows in the breaker of the illustrated type, the moving element 7 is repulsed against the fixed conductor 2 by the action of an electromagnetic force generated therebetween so that the moving element 7 is disconnected from the latter. In this case, the actuation of the switching mechanism 20 by the first contact arm 10a has a delay due to a relay time by the automatic tripping device 4. The second contact arm 10b, however, causes the second pin 16 to move away from the recess portion 14a against the force of the tension spring 17 to move in the guide hole 14 so that the second contact arm 10b rotates about the supporting shaft 12. It stops rotating when the second pin 16 collides against an end portion 14b of the guide hole 14. This repulsive movement is performed more rapidly than the operation of the switching mechanism 20 to which the moving element 7 is connected through the contact arm 10. Thus, the current limiting effect is enhanced.
Further in the case where, for example, while not shown in FIG. 1, an undervoltage tripping device is provided on an adjacent pole 1C disposed in opposition to the adjacent pole 1B so as to trip the circuit breaker when the voltage of the main circuit becomes lower than a predetermined value, an actuator (for example, 33) is attached to the opposite side (the upper side in FIG. 1) of the supporting shaft 25 so as to reset the undervoltage tripping device.
In the conventional multipole circuit breaker as described above, however, there has been a problem in that, because the supporting shaft 25 is inserted into the adjacent pole 1B through the circular hole 28 so as to couple the poles 1A and 1B with each other, the interphase insulation is lowered.
Moreover, in the conventional multipole circuit breaker as described above, because the hole 25a is formed through the supporting shaft 25 and the rivet 25b is inserted into the hole 25a so as to rivet the lever 29 and the supporting shaft 25 to each other, there have been problems that not only is the mechanical strength of the supporting shaft 25 remarkably reduced by the hole 25a, but also the fixing strength between the supporting shaft 25 and the lever 29 is reduced is the rivet 25b becomes loose.
Further, in the foregoing conventional multipole circuit breaker, when the actuator 33 is inserted and fixed onto one end portion of the supporting shaft 25, it is necessary not only to fix the actuator 33 and the supporting shaft 25 integrally with each other but to determine the attachment angle of the actuator 33 relative to the supporting shaft 25 taking the change-over point of the alarm switch 32 into consideration. Therefore, there has been a problem in that the assembly work is intricate.